#include <iostream>
using std::string;
string::size_type find_char(const string &s, char c)
{
	string::size_type i = 0;
	while(i != s.size() && s[i] != c)
	{
		i++;
	}

	return i;
}

int main()
{
	find_char("Hello world", 'z');
	return 0;
}
